SoC project suggestion

Hi folks,
Some people have asked me for more information about the Summer of
Code project to implement file system flags to scrub the data blocks
on files which have a flag associated with them. The details are to
be found here:
http://www.netbsd.org/contrib/soc-projects.html#fs_scrub_flags
To give a bit more information - this is not intended to be an
all-encompassing disk wipe/shred utility, or an implementation of
a utility to overwrite spared sectors.
Instead, I'm thinking of the number of times we delete a file, only to
have a nagging suspicion that ''rm -P'' should have been used. By the
time the thought has formed, it is too late, and the data blocks
themselves are on the freelist. The only way to overwrite the data
blocks would be to fill up all partitions on that disk to 100%, which
is not always a feasible course of action.
This project is meant to associate a system and user flag with a file
in userland, similar to the immutable flags we already have, and, on
the last unlink of the file, the data blocks would be overwritten.
It would be useful to have for shadow password files and dbs (and
temporary entries), pgp and ssh keys, and other sensitive data that a
user may have - which is where the user flag comes in. There are
various ways of doing this scrubbing, and part of this project is to
investigate this.
If you are interested in this project, which is useful without being
too complex, I'd be happy to answer questions.
Regards,
Alistair